Triangle ABC is similar to Triangle ADE because they are proportional. It is a 7:13 ratio as shown by segments CB and ED.
Therefore, the ratio from AB to AD would also have to be 7:13. The ratio as shown by the picture is x:x+8. Therefore x:x+8=7:13.
Now you put this in fraction form. = You multiply both sides by X+8 and get X=. Now you multiply both sides by 13 and get 13X=7x+56. Now you have cleared the fractions so it looks neater. Next, you subtract both sides by 7x and get 6x=56. Finally you divide both sides by 6 and get x=9 1/3